1. Field of the Invention
The present invention relates to internal combustion engines and, more particularly, to a carburetor for an internal combustion engine.
2. Prior Art
U.S. Pat. No. 4,123,480 discloses a control mechanism for a carburetor having levers connected to a throttle valve and a choke valve which engage each other. U.S. Pat. No. 4,672,929 discloses an automatic starting arrangement for a carburetor with interacting levers connected to a choke flap and a throttle flap. When the engine is cold it requires a certain amount of enrichment in the air/fuel mixture to operate. It is commonly known to use air flow choking devices or secondary enrichment circuits to provide the required enrichment during cold start. In automotive applications air choking devices were commonly used. In the beginning of the century manually activated systems were used, then thermostatic elements were implemented.
In the field of small two-stroke engines, manual choke devices are widely known. The problem found with this manually activated choke devices is the large number of users that misuse the systems that find themselves flooding the engine. Many attempts have been made to ensure the ease of use of this feature. Some of these attempts require step-by-step actions not followed by many users.
The present invention pertains to a carburetion system similar to those used in portable two-stroke internal combustion engines. The problem to overcome was allowing the enrichment system of the carburetor to operate either in idle or wide open throttle while providing simplicity of operation and low manufacturing cost. The object of the invention, allows the operator to reset the system by releasing the throttle actuator. Prior art systems provide air/fuel mixture enrichment requiring multiple step-by-step sequence of an operator""s input. Many times these prior art systems failed to operate properly due to different operator""s habits like starting the unit at idle, starting the unit at WOT, not following complicated sequence of steps, not being able to identify proper actuators"" positioning, not being able to recognize a xe2x80x9cpopxe2x80x9d signal, etc. Some prior art throttle-choke linkage system, throttle-choke latching is used to produce fast idle while the enrichment system or choke is activated. Such a system requires a trained operator who is able to learn steps not commonly used by typical users of this equipment. Less than 25% of the population of users starts the engine while at idle position, while the remaining population of users starts the engine at WOT. If not recognized or trained, over 75% of the aforementioned population of users will unintentionally deactivate the system by depressing the throttle actuator to WOT position and the engine will not start.
In accordance with one embodiment of the present invention, a carburetor control system for a carburetor comprising a first cam and a second cam. The carburetor comprises a choke valve assembly and a throttle valve assembly. The first cam is connected to the choke valve assembly. The second cam is connected to the throttle valve assembly. The second cam comprises a first section and a second section. When the first cam is moved to a choke position the first section can be contacted by the first cam to latch the second cam in a start position. When the throttle valve assembly is moved to a wide open throttle position the second section can contact the first cam to hold the first cam in the choke position.
In accordance with another embodiment of the present invention, a power tool is provided comprising an internal combustion engine which includes a carburetor comprising a choke valve, a first control member connected to the choke valve, a throttle valve, and a second control member connected to the throttle valve. The second control member has two spaced apart contact areas. The first. control member is movable relative to the second control member and, when the first control member and the choke valve are at a choke position, the two spaced apart contact areas can make respective separate contact with the first control member in at least two different positions of the throttle valve.
In accordance with another embodiment of the present invention, a carburetor is provided comprising a housing; a choke valve connected to the housing; a manually actuatable control connected to the choke valve; a first automatic control member connected to the choke valve; a throttle valve connected to the housing; and a second automatic control member connected to the throttle valve. When a user manually moves the manually actuatable control to move the choke valve to a choke position, the first automatic control can contact the second automatic control member to move the throttle valve to a first open position. When the user subsequently moves the throttle valve to a wide open throttle position, the second automatic control member contacts the first automatic control member to provide the choke valve at the choke position.
In accordance with another embodiment of the present invention, a carburetor control system is provided for a carburetor. The carburetor comprises a choke valve, a throttle valve, and a throttle control connected to the throttle valve. A positioning linkage is provided between the choke valve and the throttle valve. When a user moves the choke valve to a choke position the linkage retains the choke valve at the choke position. When the user subsequently moves the throttle control to move the throttle valve to a wide open throttle position, before the throttle valve is released to an idle position, the linkage also locates the choke valve at the choke position.
In accordance with one method of the present invention, a method of setting a carburetor for starting of an internal combustion engine is provided comprising steps of moving a choke valve to a choke position; automatically moving a throttle valve to a partially open position as the choke valve is moved to the choke position; when the throttle valve is moved to the partially open position, latching a first member connected to the choke valve to a second member connected to the throttle valve, wherein the first and second members hold the choke valve in the choke position and the throttle valve in the partially open position; and optionally subsequently moving the throttle valve to a wide open throttle position wherein the second member holds the first member and the choke valve in the choke position, wherein the choke valve can be held at the choke position by the second member when the throttle valve is at either the partially open position or the wide open throttle position.